Plastisols: An Integral Part of Modern Industry and Daily Life

What are Vinyl based plastic?

Plastisols are polymer or plastic dispersions made from polyvinyl chloride (PVC) resin and a non-drying liquid such as plasticizer. This liquid carrier keeps the PVC particles suspended and prevents the plastisol from setting until heat is applied. When heat is applied, the liquid evaporates leaving behind a solidified plastic part. Vinyl based plastic are low-cost, easy to use and can be processed at low temperatures, making them suitable for a variety of applications.

Manufacturing Process

The basic components used in making vinyl based plastic are PVC resin, plasticizer and additional additives. PVC resin is mixed with a liquid plasticizer at room temperature to form a stable slurry or dispersion. Common plasticizers used include phthalates, adipates and phosphates. Additional additives like stabilizers, pigments, fillers etc. may also be added to achieve desired properties in the final product.

The mixed plastisol is then thoroughly blended using roller mills, Cowles devices or high-shear mixers to obtain a uniform dispersion. Proper dispersion is critical as it prevents imperfections in the final product. The blended plastisol is then ready to be used in different manufacturing processes based on the end application.

Applications

Some major applications of vinyl based plastic include coatings, moldings, calendaring and lamination processes:

Coatings: Vinyl based plastic are widely used for coated fabrics in applications like automobile and furniture upholstery, tarpaulins, artificial leather, wallcoverings etc. They provide opacity, durability and flexibility to fabrics at low cost.

Molding: Vinyl based plastic can be poured or injected into molds and heated to form shaped articles. Common molded products include automobile trim parts, toys, hardware items, shoe soles and heels.

Calendaring: In calendaring, plastisol is fed between hot rollers under pressure to form sheets, films or strips. Examples include flooring vinyl, traffic line or stripping materials.

Lamination: Vinyl based plastic act as an adhesive when heat-bonded between substrate materials like fabrics, films and foams. This process is used to make anti-fatigue mats, conveyor belting, luggage and handbag liners.

Performance Benefits

Some key advantages of using vinyl based plastic include:

Low melt processing temperatures: Vinyl based plastic can be melted at temperatures as low as 150°C, avoiding thermal degradation of polymers and substrates.

Thixotropic behavior: Vinyl based plastic can be easily applied or molded but will not sag or flow after application until heat is provided.

Flexibility: The non-drying liquid carrier allows vinyl based plastic to form flexible, resilient coatings and products.

Adhesion: Vinyl based plastic adhere strongly to a wide variety of substrates like metals, fabrics, films and other plastics.

Opaque pigmentation: Opaque pigments are readily suspended to produce colored, opaque coatings and parts.

Versatility: Vinyl based plastic can be used in sheet, film and molded forms while offering properties like abrasion resistance and durability.

Sustainability Challenges
Despite their widespread use, vinyl based plastic pose some sustainability challenges:

Plasticizer leaching: Phthalate plasticizers used in vinyl based plastic may gradually leach out over time, raising environmental and health concerns.

Difficult to recycle: Due to plasticizer content, recycled plastisol waste cannot be reused in virgin applications and require special treatment.

Non-biodegradable: Vinyl based plastic are non-biodegradable and persist in the environment for long durations when discarded as waste.

In Summary, R&D is ongoing to develop more sustainable plastisols formulations using alternative plasticizers like adipates and bio-based plasticizers from renewable resources. New coating methods and additives are also enhancing plasticizer retention and allowing vinyl based plastic to be reused or more easily recycled at end-of-life. Overall, vinyl based plastic continue to play a vital industrial role, with green innovation expanding their safe and responsible use into the future.